Extreme pressure lubricant



United States Patent Ofiice EXTREME PRESSURE LUBRICANT Helen Sellei Beretvas, Chicago, Ill., assignor to Standard Oil Company, Chicago, Ill., a corporation of Indiana No Drawing. Application May 31, 1955, Serial No. 512,300

12 Claims. (Cl. 25237.2)

This invention relates to novel lubricant compositions having particular utility under extreme pressure conditions. It is particularly concerned with normally liquid extreme pressure lubricants containing complex soaps of naphthenic acid and hydroxy aromatic carboxylic acids. The use of oil soluble lead-containing soaps, e. g., lead naphthenate, lead oleate, etc., as components of extreme pressure lubricants, is well known. Particularly outstanding extreme pressure lubricants have now been prepared which contain a complex lead soap of naphthenic acid and a hydroxy aromatic carboxylic acid, the aromatic nucleus of which contains not more than carbon atoms, which nucleus has attached thereto, a carboxyl group and at least one hydroxyl group such as salicylic acid, meta and para hydroxy benzoic acids and monohydroxy naphthoic acids. By use of such complex lead soaps the extreme pressure properties of lubricating oils, containing organic sulfur compounds and usually containing chlorinecontaining extreme pressure additives, may be greatly improved over the extreme pressure properties of such oils which contain simple lead soaps such as lead naphthenate, sulfur-containing additives or chlorine-containing additives in the absence of the complex soap. It has been found that for a given weight of soap the amount of lead introduced to the oil can be increased by using the novel complex soaps instead of the simple soap, e. g., lead naphthenate. Moreover, the properties of these complex soaps have been found to be substantially more constant and not subject to the wide variation experienced with commercial lead naphthenate purchased from different suppliers.

The hydroxy aromatic carboxylic acids suitable for use in accordance herewith, are those which contain not more than 10 carbon atoms in the aromatic nucleus, and preferably not more than 6 carbon atoms in the aromatic nucleus, i. e., I prefer hydroxy benzoic acids such as salicylic acid. The hydroxyl group must be attached to the aromatic ring and also the carboxyl group must be attached directly to the aromatic nucleus. Examples of the hydroxy aromatic carboxylic acids which may be complexed to form the complex lead soaps of naphthenic acid are: salicylic acid, m-hydroxy benzoic acid, p-hydroxy benzoic acid, 2-hydroxy-1-naphthoic acid, S-hydroxy-lnaphthoic acid, 6-hydroxy-1-naphthoic acid, 7-hydroxyl-naphthoic acid, S-hydroxy-l-naphthoic acid, l-hydroxy- 2-naphthoic acid, 3-hydroxy-2-naphthoic acid, S-hydroxy- Z-naphthoic acid and 7 -hydroxy-2-naphthoic acid.

In accordance herewith, lead naphthenate is preferably reacted with litharge and a hydroxy aromatic carboxylic acid to produce the complex soap of the present invention. The present invention will, accordingly, be described with respect to such preferred method of preparation. Naphthenic acid may be used in such reaction instead of the soap. The lead naphthenate is an available article of commerce which is incompletely converted to the totally neutralized soap and hence it is usually more expedient to employ the commercial product since one-half the 2,759,893 Patented Aug. 21, 1956 double complex soap is, in eifect, already formed. Lead naphthenates containing from 25% to 35% lead are suitable, about 30% lead being preferred. It is theoretically possible that the reaction may begin with naphthenic acid and the soap of the hydroxy aromatic carboxylic acid, e. g., lead salicylate, to obtain the resultant complex soap, but the oil insolubility of the soap of the hydroxy aromatic carboxylic acid and consequent inferior contact in the reaction zone makes such method less desirable. Saponification resulting in the complex soap preferably may be initiated by a small amount of caustic soda or caustic potash, which may be added in pellet or other form in similar amount, e. g., from about 0.05% to about 2% by weight of the reaction mixture.

In preparing the complex soap it is preferred that the reaction mixture be heated to a temperature sufiiciently high and for a suflicient period of time such that a stable complex soap is formed i. e., that free hydroxy aromatic carboxylic acid does not remain in the reaction mixture. I prefer to heat about 2 mols of the hydroxy aromatic carboxylic acid per mol of litharge in the lead naphthenatelitharge mixture. I have found that the use of more than about 2 mols of the aromatic acid per mol of litharge added provides no extra increase in the extreme pressure properties of the oil containing the reaction product. I have also found that the use of about 1 mol of the acid per mol of litharge gives a product which is inferior as an additive to the complex soap produced by adding about 2 mols of the aromatic acid per mol of litharge. Thus, I use from about 1.5 mols to about 2.5 mols of the hydroxy aromatic carboxylic acid per mol of litharge in compounding the complex soap of this acid with the lead naphthenate. The heating of the reaction mixture is usually carried out for a period of at least one hour at temperatures Within the range of from about 270 to 340 F., preferably in the range of from about 300 to 320 F. The preparation of the lead naphthenate is well known to those skilled in the art and is in no way a part of the instant application.

The generally greater eifectiveness of lead fish oil soaps as extreme pressure additives, compared to lead naphthenate, is believed to be related to the relative oil insolubility of the former. Accordingly, efforts to improve the efiectiveness of lead naphthenate have resulted in the discovery that complex soaps embodying a radical of a hydroxy aromatic carboxylic acid are substantially less soluble in oil and vastly superior in their extreme pressure properties to lead naphthenate. Thus it appears that the less soluble complex soaps which may, however, still be dispersed or dissolved in a lubricating oil are the most satisfactory. Since the hydroxy aromatic carboxylic acids employed decrease oil solubility of the complex, the larger the amount of such acid in the complex the lower the solubility of the same for a given weight of soap and the more improved are the extreme pressure properties. However, the desire for a rather insoluble lead soap must be tempered by the necessity of keeping the additive in the oil i. e., producing a stable lubricant. Thus it is preferred to use a solubilizing agent in my novel extreme pressure lubricant. In this connection, it has been found that oleic acid is especially effective in solubilizing the complex soaps which are difiicultly soluble. The oleic acid may be used in amounts within the range of 1% and 7%, preferably 2% to about 3% by weight in the composition. Solvent extracts, i. e., extracts obtained by extracting lubricating oils base stock with phenol, fulfural, chlorex, etc., are also excellent solubilizers for use with the complex soaps. These extracts may be used in amounts within the range of from about 5 to about 40%, preferably 20% to 30% of extract solubilizer based on the total weight of the lubricating composition.

I have also found that an alkyl phenol, e.g., nonyl phenol or other alkyl phenols having a total of 8 to 12 carbon atoms in no more than 2 alkyl side chains and no such side chain containing less than 4 carbon atoms is effective as a solubilizing agent for the complex soaps, Such alkyl phenols may be used in amounts of 1.0 to by weight in the extreme pressure lubricant. Lead naphthenate as such, which may be used in amounts of 1.0 to 10% by weight of the composition, is useful as a solubilizing agent and is particularly advantageous from the standpoint of introducing still greater quantitie of lead to the lubricant.

As will be apparent from the data set forth in Table l oleic acid has a special utility in extreme pressure lubricants of the type herein described over and above its mere sclubilizing influence upon the complex soap. The increased extreme pressure properties of the oil containing oleic acid is noted generally when the complex soap or lead naphthenate as such is present in the oil along with the other additives. ferred lubricant composition of this invention, there is employed conjunction with the complex soap and a sulfurized and chlorinated extreme pressure additive, at least about 1% oleic acid, by weight, based on a total lubricant and preferably from about 2% to about 3%. As nuch as 7% or more may be used but the resulting improvement, if any, compared to the cost, is ordinarily not justifiable.

In accordance with the preferred embodiment of the present invention, the complex soaps are prepared by combining litharge and lead naphthenate in a ratio by weight of from about 1:2 to about 1:5 and preferably about 1 part or" litharge per 4 parts by weight of lead naphthenate. The hydroxy aromatic carboxylic acid component of the complex is employed in an amount from about 1.5 to about 2.5 mols of the acid per mol of litharge and preferably about 2 mols of the hydroxy aromatic carboxylic acid per mol of litharge in the reaction mixture. As indicated above, the reaction mixture is heated to a temperature within the range of from about 270 to 340 F., preferably about 300 to 320 F. Thus I have found when employing as high as 4 mols of acid per mol of litharge a soap of undesirable liquid consistency is formed. I have also found that when using a mol ratio as low as approximately 1:1 acid to litharge substantially no improvement in the extreme pressure properties is realized over an oil containing lead naphthenate, sulfurized sperm oil, chlorinated hydrocarbons and oleic acid.

The complex soaps of the present invention are primarily useful in heavier lubricating oils of the type employed for extreme pressure use, preferably mineral lubricating oils having a viscosity at 210 F. of at least about SSU and preferably about 75 to about 115 SSU. The soaps are not limited in their utility to such oils for the fabrication of extreme pressure lubricants but may be used with oils having lower as well as higher viscosities. Such oils may be acid-treated, solvent-extracted, etc., without in any way departing from the scope of this invention. Non-solvent extracted, acid-treated (sulfuric acid) oils are preferred for use in accordance herewith. The complex soaps of the present invention are also useful in synthetic lubricating oils such as ester type synthetic oils and the silicone oils.

The amount of the novel soaps, described herein which are to be employed in extreme pressure lubricants, will vary over a wide range depending upon the type of oil, other additives employed therewith, the intended application of the particular lubricant, etc., but generally an amount of from about 1 to about 10% by Weight based on the total lubricant and preferably from about 3 to about 7% by weight, has been found desirable.

For the purpose of illustrating the preparation of the novel complex soaps of the present invention, but without any intention of being limited to the specific illustrative example set forth, the following example is presented:

900 grams of commercial grade lead naphthenate con- Hence, in accordance with the pretaining 30% lead, obtained from Harshaw Chemical Company was heated to 300 F. to which lead naphthenate was then gradually added 225 grams of litharge. To this heated mixture was added 10 pellets of potassium hydroxide weighing a total of about 1.5 grams and the mixture was stirred mechanically for a half hour while the temperature of the mixture was held between about 270 and 340 F. At the end of the half hour period 255 grams of salicylic acid was added to the mixture to form a complex soap and the resulting mixture was heated for an additional period of one hour at a temperature within the range of 300 to 320 F. A grayish-brown soap resulted which was of tafiy-like consistency, which soap upon analysis, showed a lead content of 33.7% lead. A part of this soap was blended with the oleic acid in the ratio of 60 parts by weight of soap to 40 parts by weight of oleic acid in order to prepare extreme pressure lubricants containing the complex soap and also free oleic acid.

In order to determine, in the laboratory, the effectiveness of the complex soap prepared in accordance with the foregoing sample, tests were run in both the Timken and Shell. four-ball extreme pressure testing machines. Each of these testing machines is useful in the laboratory evaluation of extreme pressure lubricants but they are dissimilar in their method of testing and in the results obtainable therefrom. Thus, oil will often show up well in one test but not on the other. However, lubricating engineers, while not entirely in agreement as to the exact meaning of these tests when translated into actual performance, have been able to correlate these tests to a certain effect and in general find them most useful in evaluating new lubricant compositions.

The Timken machine is well known to those skilled in the art and it is unnecessary here to describe the same in detail since they are fully described in the Journal of Institute of Petroleum, 32, pp. 209210 and 220-222 (1946). The Shell Four-Ball testing machine is likewise well known to those skilled in the art for its utility in evaluating hypoid lubricants and is likewise described in detail in the literature, National Petroleum News, 31, p. 52 (December 27, 1939) p. R551 and also Journal of the Institute of Petroleum, 32, pp. 210-212 and 222-23.

Set forth in Table 1 are the results of tests in the Timken machine which demonstrate the improvement obtained by employing novel soaps of the present invention in lubricating oil base stock in comparison with the use of lead naphthenate, chlorinated hydrocarbon, sulfurized sperm oil and oleic acid separately and in the base stock containing all of these known extreme pressure additives. In each of the tests set forth in Table 1, a lubricating base oil consisting of a non-solvent extracted SAE SO-grade mineral oil'was used, to which base oil was added the lead naphthenate-salicylic acid complex, lead naphthenate, oleic acid, chlorinated hydrocarbon and sulfurized sperm oil as indicated in the table. The lead naphthenate-sali cylic acid complex soap component was the complex soap prepared in the above example. The ultimate lubricant in each of the experiments of the table had a viscosity at 210 F. between about and 98 SSU. The chlorinated hydrocarbon used was a commercial product (CH73) obtained from Pennsylvania Salt Manufacturing Company and contained 73% chlorine. The lead naphthenate was a commercial product containing 30% lead, the same product as used as an intermediate in producing the complex soap of the above example. The sulfur-containing additive, i. e., sulfurized oil was a commercial-sulfurized sperm oil-containing from 10 to 13% combined sulfur.

The striking improvement in the Timken results, when employing the novel complex soap of the present invention, is demonstrated in Table 1.

In Table 2 tests in the Shell Four-Ball tester further demonstrate the improvement obtained with the complex soap as compared to lead naphthenate. No sulfur-containing or chlorine-containing additives were employed in these compositions. Hence, in these tests the effectiveness of'the complex soap as the sole additive is demonstrated. The lubricating oil base stock was the same as used for the compositions of Table 1, that is, acid-treated SAE 50 base oil. The lead naphthenate and oleic acid additives were samples of the same commercial products used in preparing test samples, the results of which are shown in Table 1. The complex soaps used in Examples 2 and 4 were samples of the complex soap of lead naphthenate and salicylic acid prepared in the above example. The complex soap of Example 3 was prepared in the same way except that 339 grams of litharge was used to provide essentially a 1 to 1 ratio of salicylic acid to litharge.

Table 1 Com- Pb Chlo- Sulfur- Timken plex naph- Oleic rinated ized Tests Test Soap thenate Acid Hydro- Oil (Per- (Per- (Percarbon (Percent) cent) cent) (Percent) cent) Pass Fail 1 (Oontrl) None None None None None 15 18 2 3 5 95 100 6 5 55 60 3 5 85 90 3 5 50 55 None None 30 35 None None 15 18 None 30 35 None 5 40 45 1 M01 ratio salicylic acid to litharge=L83 to 1. 2 Mol ratio salicylic acid to litharge=L00 to 1.0.

Table 2 Percent Pb Naph- Percent Percent Shell Four Test thenate Complex leic Ball Weld (30% Pb) Soap Acid Point, Kg.

1 (Control) None None None 100 2 4. 2 None None 180 4. 2 None 2.8 180 None 4. 2 None 220 The above data in Table 2 indicate improvement obtainable with a complex lead naphthenate-salicylic acid soap and demonstrate the improved results obtainable when using the lead naphthenate-salicylic acid complex soap as the only additive. The use of oleic acid when added to the base oil containing lead naphthenate gives no improvement over the oil containing the lead naphthenate alone. The addition of the complex lead soap of naphthenic acid and salicylic acid alone gives a marked increase in extreme pressure properties in the Shell Four- Ball weld-point test over the increase obtained with lead naphthenate alone or when oleic acid is present with the lead naphthenate.

The complexes of other aromatic acids with lead naphthenate were made and tested. Thus, a complex soap was prepared according to the procedure of the above example substituting cinnamic acid for the salicylic acid. This complex was added to the base oil in amount of 4.8% along with 2.8% of oleic acid, 5% of sulfurized sperm oil and 3% of the chlorinated hydrocarbon (CH- 73). The Timken results showed a passing value of 50 lbs., and a failure at 55 lbs., i. e., the same results obtained in Experiment 5 of Table 1 wherein lead naphthenate was used. The substitution of the lead naphthenate-benzoic acid complex soap for the lead naphthenate-salicylate soap in the base oil containing 5% of the sulfurized sperm oil, 3% of the chlorinated hydrocarbon and 2.8% of oleic acid showed a passing load of 55 lbs., and a failure at 60 lbs., in the Timken test.

Although the specific materials employed in the test set forth in Table 1 were sulfurized sperm oil and a chlorinated hydrocarbon, it should be understood that many other known sulfur and/ or chlorine-containing materials may be employed in conjunction with the complex lead soaps of the present invention. Thus, sulfurized hydrocarbons, sulfurized carboxylic acid, e. g.,

sulfun'zed tall oil, sulfurized oleic acid, etc., organic sulfides, sulfurized vegetable oils, polysulfides, e. g., the dialkyl, tri-, tetra-, penta-, and hexasulfides, and other oil soluble sulfur-containing compounds or materials useful in extreme pressure lubricants may be employed alone or in combination with each other in accordance herewith. Reference is made to U. S. 2,136,391, U. S. 2,202,394, and many other patents disclosing sulfur-containing additives to obtain extreme pressure properties. Such materials are generally useful in accordance herewith. The sulfur-containing organic substituents of this invention for use in combination with the complex soaps are employed in the extreme pressure lubricant in an amount sufficient to afford a lubricant sulfur content of from about .3% to 3%. Thus, an amount of sulfur-containing organic extreme pressure additive of from about 1 to about 15% and preferably from about 3% to about 10% may be employed. Likewise, chlorinated compounds of various types may be employed in lubricants containing the novel complexes. Thus, chlorinated hydrocarbons have been employed, which, for example, may be obtained by chlorinating paraifin wax or olefininc hydrocarbons. Individual chlorinated aliphatic compounds such as hexachloroethane, heptachloropropane, octachlorobutane and so forth are useful. Reference is made to U. S. 2,178,513 which sets forth a substantial number of halogenated ring compounds which are useful in extreme pressure lubricants. Such materials may be employed as the chlorinated hydrocarbon in accordance with the present invention. U. S. 2,276,341 also discloses large numbers of chlorinated hydrocarbons and organic materials which may be used. The chlorine-containing extreme pressure agents or additives are employed in the extreme pressure lubricants in an amount sufiicient to afford a chlorine content of from about 1% to about 6%, preferably from about 2% to about 5% chlorine. An amount of chlorine-containing extreme pressure additive of from about 1% to about 8% and preferably from about 2% to about 6% may be employed. As indicated above, from about 1% to about 10% of a complex soap is added to the lubricant, preferably from about 3% to about 7%. In addition to the solubilizing agent, sulfurized material, chlorinated hydrocarbon and lead-containing materials disclosed hereinabove, it should be understood that lubricants containing the same may also have added thereto typical lubricant oil additives such as anti-oxidants, oiliness agents, corrosion inhibitors, detergents, etc. In particular, phosphorous-containing compounds often employed in extreme pressure lubricants may be employed. A particularly useful phosphorous-containing material is that resulting from a treatment of a hydrocarbon, e. g., an olefin polymer with a phosphorous sulfide. Other phosphorouscontaining compounds useful in lubricants of this kind may also be employed. As indicated above, lead naphthenate may be employed in addition to the lead complexes of the present invention. Likewise, other lead soaps such as lead oleate, lead tallate and lead soaps of various high molecular weight, oil-soluble carboxylic acids which do not substantially affect the viscosity of the lubricant, i. e., do not substantially thicken or gel the lubricant may be employed in conjunction with the novel complexes of the present invention. Moreover, the lead soaps may themselves be sulfurized, e. g., sulfurized lead tallate, and used in conjunction with the complex soaps of the present invention.

Percentages recited herein and in the appended claims are by weight unless otherwise indicated.

Having thus described my invention, I claim:

1. A normally liquid extreme pressure lubricant comprising a lubricating oil and a minor amount of a complex lead soap of naphthenic acid and an hydroxy aromatic carboxylic acid, the aromatic nucleus of which contains not more than 10 carbon atoms, said nucleus having attached thereto a carboxyl group and attached to said aromatic nucleus at least one hydroxyl group, said complex lead soap being prepared by heating a mixture of from about two parts to five parts by weight of lead naphthenate per part by weight of'litharge in the presence of from about 1.5 mols to about 2.5 mols of an hydroxy aromatic carboxylic acid per mol of litharge in said mixture.

2. The normally liquid extreme pressure lubricant of claim 1 wherein the lubricant oil is a mineral lubricating oil.

3. The complex lead soap of claim 1 wherein the hydroxy aromatic carboxylic acid is a hydroxy benzoic acid.

4. The complex lead soap of claim 3 wherein the hydroxy benzoic acid is a salicylic acid.

5. The lubricant of claim 1 which contains from about 1% to about 7% of oleic acid.

6. The lubricant of claim 1 which contains a quantity of sulfur-containing organic constituents eifective to improve the extreme pressure properties of said lubricant.

7. The lubricant of claim 1 which contains a quantity of sulfur-containing constituents and chlorine-containing constituents effective to improve the extreme pressure properties of said lubricant.

8. A normally liquid extreme pressure lubricant comprising a major proportion of mineral lubricating oil, a minor amount of a sulfur-containing organic material effective to improve extreme pressure properties of said lubricant, and from about 1 to about 10% of a complex lead soap of naphthenic acid and salicylic acid, said complex lead soap being prepared by heating a mixture of from about 2 parts to 5 parts by weight of lead naphthenate per part by weight of litharge in the presence of from about 1.5 mols to about 2.5 mols of salicylic acid per mol of litharge in said mixture.

Percent Complex lead soap of naphthenic acid and salicylic acid 3 to 7 Organic sulfur-containing E. P. additive 3 to 10 Organic chlorine-containing E. P. additive 2 to 6 Oleic acid 2 to 3 said complex lead soap being prepared by heating at a temperature within the range of 270-340 F. a mixture containing lead naphthenate of about 30% by weight lead content and containing litharge in the ratio of about 4 parts by weight of said lead naphthenate to 1 part by weight of litharge, said mixture also containing from about 1.5 to 2.5 mols of salicylic acid per mol of litharge in said mixture.

References Cited in the file of this patent UNITED STATES PATENTS 2,322,307 Neeley et al. June 22, 1943 2,472,503 Minne June 7, 1949 2,599,553 Hotten June 10, 1952 2,720,491 Beretvas Oct. 11, 1955 

1. A NORMALLY LIQUID EXTREME PRESSURE LUBRICANT COMPRISING A LUBRICATING OIL AND A MINOR AMOUNT OF A COMPLEX LEAD SOAP OF NAPHTHENIC ACID AND AN HYDROXY AROMATIC CARBOXYLIC ACID, THE AROMATIC NUCLEUS OF WHICH CONTAINS NOT MORE THAN 10 CARBON ATOMS, SAID NUCLEUS HAVING ATTACHED THERETO A CARBOXYL GROUP AND ATTACHED TO SAID AROMATIC NUCLEUS AT LEAST ONE HYDROXYL GROUP, SAID COMPLEX LEAD SOAP BEING PREPARED BY HEATING A MIXTURE OF FROM ABOUT TWO PARTS TO FIVE PARTS BY WEIGHT OF LEAD NAPHTHENATE PER PART BY WEIGHT OF LITHARGE IN THE PRESSENCE OF FROM ABOUT 1.5 MOLS TO ABOT 2.5 MOLS OF AN HYDROXY AROMATIC CARBOXYLIC ACID PER MOL OF LITHARGE IN SAID MIXTURE. 